Hydrofluoroolefins (HFOs), such as tetrafluoropropenes (including 2,3,3,3-tetrafluoropropene (HFO-1234yf)), are known to be effective refrigerants, heat transfer media, propellants, foaming agents, blowing agents, gaseous dielectrics, sterilant carriers, polymerization media, particulate removal fluids, carrier fluids, buffing abrasive agents, displacement drying agents and power cycle working fluids. Unlike chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), both of which potentially damage the Earth's ozone layer, HFOs do not contain chlorine and, thus, pose no threat to the ozone layer. HFO-1234yf has also been shown to be a low global warming compound with low toxicity and, hence, can meet increasingly stringent requirements for refrigerants in mobile air conditioning. Accordingly, compositions containing HFO-1234yf are among the materials being developed for use in many of the aforementioned applications.
One manufacturing process for HFO-1234yf, as disclosed in U.S. Pat. No. 8,058,486, the contents of which are incorporated herein by reference, uses 1,1,2,3-tetrachloropropene (1230xa) as starting raw material. The process consists of the following three steps:                1) 1230xa+3HF→2-chloro-3,3,3,-tritluoropropene (HCFO-1233xf)+3HCl in a vapor phase reactor charged with a solid catalyst,        2) 1233xf+HF→2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) in a liquid phase reactor charged with a liquid catalyst; and        3) 244bb→2,3,3,3-tetrafluoropropene (HFO-1234yf)+HCl in a vapor phase reactor.        
In one process, Step (1) occurs in the presence of fluorination catalyst, such as chromium oxide and the like, as known in the art. While this catalyst is generally quite active and selective, it tends to deactivate (lose activity) slowly over time during the course of the reaction. Deactivation, in turn, leads to yield loss and a process that is economically disadvantageous.
Thus, there is a continuing need for a reactor systems and processes that extend catalyst life and stability in, among other things, the conversion of 1230xa to 1233xf.